Brandishing a loudspeaker, Guaido told thousands of supporters he would embark on a tour of the country before leading a nationwide march on the capital.
"Once we've finished the tour, the organization in every state, we'll announce the date when all together we'll come to Caracas," said the 35-year-old leader of the legislature, who is recognized as interim president by more than 50 countries.
"Miraflores, Miraflores!" chanted Guaido's supporters in response, a reference to the presidential palace currently occupied by Maduro.
Guaido threatened to call on outside intervention "when the time comes," pointing to the constitution, which authorizes "the use of a Venezuelan military mission abroad, or foreigners inside the country."
"Intervention, intervention!" cried his supporters.
"All the options are on the table," added the National Assembly president, using a phrase employed by US President Donald Trump, who has consistently refused to rule out a military intervention in Venezuela.
'We will never surrender'
Guaido was speaking from the back of a pick-up truck after security services prevented the opposition from setting up a stage at their original protest site, arresting three people.
Some 20 armored anti-riot vehicles were stationed on a highway that leads to the main avenue in the east of Caracas, where the opposition march was due to take place.
Guaido is trying to force out Maduro — whose May re-election he deems illegitimate — in order to set up new polls. (READ: Maduro wins as rivals call for new Venezuela elections)
Maduro also called out his supporters to protest against "imperialism" in a march that marks four years since the United States branded Venezuela a "threat" to its security and imposed sanctions.
"Today, more than ever, we're anti-imperialists. We will never surrender!" Maduro wrote on Twitter.
The mounting political pressure comes as authorities struggled to restore power following a major electricity outage that began on Thursday afternoon.
Maduro told supporters that almost 70% of power had been restored but at midday there was another cyber "attack at one of the generators that was working perfectly and that disturbed and undid everything we had achieved."
Although Caracas and the states of Miranda and Vargas — home to the country's international airport and main port — had intermittent power, the western regions of Barinas, Tachira and Zulia remained without electricity.
It was one of the worst and longest blackouts in recent memory in Venezuela and paralyzed most of the country.
Communications Minister Jorge Rodriguez blamed it on a cyber attack against the automated control system in the central generator at the Guri hydroelectric plant in the country's south, which serves 80 percent of Venezuela.
Hospitals had reported terrible problems and those with generators were using them only in emergencies, while flights were canceled, leaving hundreds of travelers stranded at airports.
The Caracas subway, which transports two million people a day, remained suspended and shops were closed.
"The problem is food, I'd bought meat and it's going bad. I'm going to the march because we need change. We're fed up," Luis Alvarez, a 51-year-old truck driver, told Agence France-Presse.
'I share the despair'
Venezuela has suffered more than four years of recession that has seen poverty soar as citizens struggle with food and medicine shortages.
Problems have been exacerbated by hyperinflation the International Monetary Fund says will reach 10 million percent this year.
An estimated 2.7 million people have left the country since 2015.
"I share the feeling of despair, I have lost relatives due to the lack of medicine," said Guaido, who told supporters that "there's no other option to get out of this without street mobilization."
During the blackout, witnesses described scenes of chaos at several hospitals as people tried to move sick relatives in the dark to clinics with better emergency power facilities.
Ecuador's foreign ministry issued a statement claiming 79 Venezuelans had died as a result of the power cut, which Rodriguez denied.
Critics blame the government for failing to invest in maintaining the electrical grid, although authorities often points the finger at external factors when the lights go out. – Rappler.com